The present invention relates to a shaft-sealing device and, more particularly, to a magnetic fluid shaft-sealing device with at least one seal ring to form at least one seal for a pump.
It is well known to mount a mechanical seal or a magnetic fluid seal in a pump for sealing between a pump housing of the pump and a rotary shaft in the pump housing. A typical magnetic fluid seal device generally includes a plurality of annular magnets mounted in an interior of the pump housing and around the rotary shaft or a shaft sleeve. Each magnet is sandwiched between two pole pieces also mounted around the rotary shaft. A magnetic liquid is filled in a sealing gap between an outer periphery of the rotary shaft and inner peripheries of the pole pieces. The rotary shaft and the poles pieces are made of magnetizable material. A closed magnetic circuit with magnetic force is created by flows of magnetic field lines from the magnets through the poles pieces, the rotary shaft, and the magnetic liquid and, thus, retains the magnetic liquid in the sealing gap to provide a sealing effect between the pump housing and the rotary shaft. The sealing effect of the magnetic fluid seal device mainly depends on the ability of keeping the magnetic liquid in the sealing gap. However, due to centrifugal force generated during rotation of the rotary shaft, the pumped medium or coolant in the pump tends to infiltrate into the sealing gap between the rotary shaft and the poles pieces, and the magnetic liquid in the sealing gap tends to leak outward. Further, assembly and maintenance of the typical magnetic fluid seal are inconvenient.
Thus, a need exists for a magnetic fluid seal device that can securely retain the magnetic liquid in the sealing gap while preventing the pumped medium or coolant in the pump from infiltrating into the sealing gap.